The possible functional relationship between protein kinase activation and effects of analogs of cAMP on growth rate, DNA synthesis and enzyme induction will be examined in cultured hepatoma cells. A number of these 6- and 8-substituted analogs will be tested under a variety of conditions to determine whether a correlation exists among the changes brought about in these metabolic parameters. Protein kinase activity in vivo will be assessed by isolation of the tryptic peptide from f sub 1 histone containing the serine residue subject to cAMP-dependent phosphorylation after incubation of cells with PO432 equals or PO433 equals with or without analogs. The ability of analogs to be hydrolyzed by phosphodiesterase will be analyzed with cell extracts as a source of enzyme. Metabolism of analogs in vivo will also be investigated. Of particular interest will be analogs which are highly potent and which are resistant to phosphodiesterase attack. The inhibitory effects of N6, O2'-dibutyryl cAMP on DNA synthesis have been shown to result from a reduction in the steady state pools of dTTP and dCTP. Consequently, enzymes involved in deoxyribopyrimidine nucleotide metabolism will be assayed to determine whether any of them exhibit a change in activity after exposure of whole cells to cAMP analogs. Ultimately it is hoped that these diverse metabolic effects of cAMP analogs can be functionally integrated into a cause and effect relationship. The possibility that protein kinase represents the common denominator in all these responses should be decided by the outcome of these studies.